Viewers of Peppa Pig were shocked when the children's cartoon was interrupted by the image of a woman with her hands down her pants.

The incident occurred on channel FOUR just before 3pm today.

Margaret Lewis, of Paraparaumu, said she was on Skype with her daughter and 16-month-old granddaughter, who had Peppa Pig on the television in the background.

"Next thing there was a still of a woman ... with her hands down her pants, and next to her was another picture where she's licking her fingers."

It stayed up for at least a minute, and later came back on for about 10 seconds, she said.

"We're just bloody shocked, has it been hacked?"

Daughter Jessie McGee, of Palmerston North, said she was not impressed.

"This is prime time for preschool TV."

She would consider making a complaint, she said.

"If that was a 'mild photo', if they could do that twice in preschool hours, could you imagine what else someone could put up there?"

Other parents took to FOUR's Facebook page after the episode aired.

"Can we have an explanation in regards to the inappropriate pictures flashing up on screen during peppa pig this afternoon?? Neither myself or my daughter (who is THREE) were impressed!," wrote one.

Another said: "What the flip FOUR, my son was watching Peppa Pig just now and right before it ended, a picture of some woman with her hands down her pants and one of her eating her hands or something pop's up on the screen and stays there for at least 1 minute. WHY ARE YOU PUTTING STUFF LIKE THAT ON DURING CHILDREN'S PROGRAMMING?????''

Channel FOUR broadcaster MediaWorks has apologised for the blunder.

"As a result of human error, a graphic intended for another programme was mistakenly broadcast within Peppa Pig today," spokeswoman Rachel Lorimer said.

"We take our responsibilities as a broadcaster seriously, and apologise unreservedly for the mistake. We are taking steps to ensure this does not happen in future."